Herald’s high level design is documentated in diagram form in our Archi HTML export. The raw archi file can be downloaded from GitHub.
The best diagram to start with is the Masters views index. Note that all diagrams can be clicked to open up new diagrams and entity information.
We deliberately don’t use Archimate to provide UML style class diagrams. We use agile development and so keeping diagrams up to date with live code would be a foolhardy exercise.
Instead we provide Doxygen documentation for the C++ reference implementation API. Each class here shows its inheritance diagram.
If you think some documentation is missing, please head on over to #herald-general on the LFPH Slack or open a new Feature request on GitHub.
To help you get started, see the documentation.